Propeller control



June l2, 1951 R. E. MOORE ETAL PROPELLER CONTROL 3 Sheets-Sheet l Filed April 23, 1949 IN V EN TORS R/CHAQD E. Moo/a5 BY .DAV/D A. P/cH/mvso/v THEIR 66. SMM.

June 12, 1951 R. E. MOORE ET A1. 25569700 PROPELLER CONTROL Filed April 2s, 1949 s sheets-sheet 2 INVENTORS F/CHA/:D E Moo/PE BY .DHV/D /JilcH/QPDSON rms/.e HrTon/vc ya June 12, 1951 R. E. MOORE ETAL 2,556,700

PROPELLER CONTROL Filed April 23, 1949 3 Sheets-Sheet 5 1N VEN ToR Plc/Lm @D Moa/PE Dn v/D A. R/cHAeDsa/v Patented June 12, 1951 STATES ,2,555,700 PROPELLER coN'rRQL richard-anatre,Dayton, onorare Richardson, Broomall, Pa.,

erai'Mtors cofparatiqp, permitiran.; :Mr-

poration of Delaware ApplicationLApril 23,

9 Claims.

bladeA allele charges 0f. eensiderable magnitude.

vIt is aprineipeliebiet ef. .thefinventien to provide .fdr charge of the aceumulater while-the prepeller :is in Q Deratien butv Wthvut interfering withthejuid eircuitvfeeding the blade angle controlI means.

A furtherobiect of -thevinvention is to provide for accumulatorcharge that does not take rvall ofthe-available ilow While blade angle or pitch change is required.

v.Another vobject of theinvention is toprovide a system in whichtheventire yvolume of the accumulatorvwill be available if necessary to complete the function called for.

'Another object of the invention is to provide trip means formaintaining accumulator connectionvto the systemthough the system pressure is the higher.

E Cet another object Vof* the invention is tov-providefor applying'the accumulator pressure to the system such -that l.itwill not be liinitedfor controlled byl the pressure controlvalve offthesysteni.

Further objects, and `,advantages of the present invention` will be lapparent from the -following description, reference .being hadv to the accom- E31yng drawings wherein a `preferred embodiment of the present invention is clearly shown.

AIn' the drawings: y

Fig. l a schematiefview of the-fluid cireuit for controlling a propeller, lwithfcontrolled pressuref in the pressure line, and a branch line fior i charging an accumulator under the control of a trip valve selectively admitting the accumulator pressure to the pressure line. y

Fie-.- 21s a Similar View, embodying e-mede'd ferm of accumulator control valve. l

Figs. 3 and 4 represent altered positions ofthe controlvalves for the accumulator, shown in Figs. 1 and 2respectively.

Fig 5 i s a schematic sectional view longitudinally vof a, propeller mechanisinernbodying the subi ectginvention, particularly the circuit Y shown in- Eie. 1-

AIn iiuidpressure controlled lvariable pitchfpropellers regulation ofthe pitch tomatch the propeller thrust 4to the power .being applied: by .le engineis effected by thefresponse of a valve, which may be a governor valve *of several types, that distributes; rneasnred amountsk of fluid .under pressureio Aone side oranother of a'blade operatinggergvomotor. There are'alsoeninstancesfwhen I 1949,..se1=ia,i No. 89,192

(c1. fio-51) ereaeesmer Q90@ A iveifilfnire4 emmer also weer rzhilenthe buter Valve iS aplyig rneasnredamerrite-Qf ridlieresre, er is in 'other Weide @snellire- .thetlasie .setting It is' therefore esseritielAthatl resrve'of'fluid under pressurebeabuiltlupr; ui and ir'r1ai'ritained at all l dernands Athat would Aentre*iii-the diiculties are to be h difficulties by prourripwith a pressure o1. apparatus, and inprssurei/alve in that es'sureof' paper eotreleelle er trol, valvermear be eveilaleletor, millater .eentrbl accumulator-'and lectivelyfeonnects it with the pressureli e,4 bybyLpassing ftlieV rninirnum pressure `and thev'va Jble pressure control valves. Thusiaccuinii to ejand application to the s Y s e stherevby independent ofthe presfeentrelfmeanse Y VNVith vdetailed 4,reiererivce Lto Vthe drawings, I referstofr m uirlp'.witl'i intakeva't '2'V and which .delivers Iiderpressure through outletl 3 and ai'lterfll toa/chamber Il o f a mini- `A .opens'byt into an the niiniiuinpressure valve I2 1 connects with acheck valve nds )o y'Zlltda .governor distributor valve', "g outlets 33 l'and'32 leadingA to opposite sideso ab derzshift ygserv'oinotcr'lill whose piston# actu tes gea 42turninga bladef43 about its pitch Tapped into the pressure -l-ifne f2, ,y tween the ininirnum 'pressure valve `ll'arldfthefeh .ck-,velvelthereie a branch passage fzzfeenneetine .with a chamber .23 of .the variable 'pressure vvalve' 0 Whosevliable control is empletedfby afeedfbeCk-'liels extending f ronivzthe -pitohincreaseline 3|. The .part 5 is providedfvgith 'a 'restriction Blthat SlOWs up ow of 'uid -rrin tHe-'bump vI injitsrassaiee through vid storage device.

avesself dividedbv a' im la pressure Cherriag'e ,1 chamber '.63 always instant s inveltion attains the objects andy open to passage 8 which is branched at 64 to connect with an accumulator control Valve assembly 1G, 80 for selectively applying accumulator pressure through 24 to the pressure line 2l at a point between the check valve 25 and the distributor valve 30. Selective control of the accumulator pressure control valve is eiected by manual operated means 9E! as Will presently appear.

A minimum pressure is established in the pressure outlet 3, due to the action of the valve unit I. The chamber II is tted with a plunger I3 headed at I4 to span the bore of the chamber II, the stem having a. bore 'I5 opening from the face of the head I4 and opening by passages I5 to the outside of the stem to be in communication with the passages 3 and 5. A spring II in the chamber II disposed about the stem I3 tends to move the head I4 toward the end of the chamber to which is connected the pressure line I2, there being spacing pads I8 to provide a slight spacing between the head and end of chamber II for pressure application from the bore I5. In operation, when the pump I is operating the output builds up pressure in chamber I I that is also existent in the passage 5 leading to the restriction S, and in the bore I5 of the stem which exerts itself against the whole area of the plunger head I4, which is opposed only by the same pressure against an annular area of the head I4 around the stem I3, plus the force of the spring l'I and centrifugal force acting on the plunger and head due to the propeller rotation. The result is that the build-up of pressure will eventually move the head I4 away from the end of the chamber to open the passage into the pressure line I2, thereby establishing a minimum of pressure potential in the passage 3, 5 before any pressure potential appears in the pressure line I2.

That minimum of pressure potential is provided for distribution to the blade shifting servo-motor by means of the distributor valve 30 after moving from the accumulator through the control valve assembly. The fluid under pressure in the line I2 ilows through the check valve 20 by displacing the ball check 25 against the spring 26 and ows on through 2| tothe pressure supply port 34 of a sleeve 35 providing the ports 3I and 32. A speed responsive plunger 36 has lands 31 and 33 so spaced as normally to cover the ports 3i and 32 respectively, the end of the plunger 36 being pivotally joined to a lever 39 for transmitting spring force to the Valve plunger 36 in opposition to centrifugal force resulting from rotation of the propeller on which the control mechanism is mounted. In the drawings the distributor valve 35 is illustrated in the equilibrium position in which the lands 3'I and 38 stop flow of :duid from the pressure supply port 34 to either of the pitch change ports 3l and 32. Under those conditions there is no appreciable relief for the pressure that is being built up in the pressure line I2, 2i due to the continued operation of the pump I. In this equilibrium position of the distributor valve the build-up of pressure is felt all along the way through the passages 3, 4, 5, 6, 'I and 8 to the accumulator, and all along the Way through the chamber II, I2 and 22 to the chamber 23 of the variable pressure control valve which determines the maximum limit to which the line pressure can reach at any time. It should be apparent, that movement of the distributor valve plunger 3B in either direction along the sleeve 35 from the position closing the ports 3| and 32 will tend to relieve the pressure built up in the line I2, 2 I. Any movement of 36 from the port covern the reservoir.

ing position permits uid under pressure to flow from port 34 to either port 3I or 32 and thence by either passage 44 or 45 to one side or the other o the piston 4I of the servo-motor 40. Thus, the system must not only provide means for protecting the fluid pressure lines against damage from excessive pressure, but must also be provided with means for insuring that there will be sucient pressure available in the pressure line at all times to completely and quickly perform any degree of operation called for by the distributor valve.

The variable pressure control valve provides suiicient control over the potential of pressure in the pressure line during the normal propeller operating conditions even though of the most critical demands, and the accumulator with its control mechanism are sufficient to take care of any emergency, as will presently appear. The build-up of pressure in the pressure line I2 is applied through 22 to chamber 23 of the unit 50,

which chamber is traversed by a plunger 5I carry-v ing lands 5Ia and 5Ib and damping head 5Ic engaged by a spring 52 and seated on a shoulder 23a joining a reduced bore 23h surrounding the lands 5m and 5Ib. From the chamber 23 a passage 23e extends to a chamber 23d into which projects the stem 53 of a headed plunger 53a. urged by a spring 53h to close a relief passage 53e. Upon the rise of pressure to an excessive value, the plunger 53 will be moved downward to establish communication between chamber 23d and relief passage 53c, which spills back into the reservoir supplying the intake 2 of the pump.

The pressure within the system rarely reaches that point of blow-off due to the action of plunger 5I in rst relieving pressure from the chamber 23 through port 54 and 54a to the reservoir, because the pressure in chamber 23 applies to the annular area around the plunger 5I against the end of the land 5Ia and opposes the force of spring 52 and centrifugal force on the plunger assembly tending to move the plunger and lands toward the top of the view. When the pressure on that annular area predominates the plunger 5I moves downward and uncovers the blow-off port 54 which reduces the pressure in chamber 23 and consequently the pressure in the line I2. That reduction of pressure is Variably resisted by an additional force applied from the pitch increase line 44 through the passage 33 that opens into the reduced bore 23b housing the spaced lands 5Ia and 5Ib. A neck portion between the lands Ela and 5Ib is apertured at 5Id to open into an axial bore 5Ie communicating with a chamber 5If of the reduced bore 23, making it possible for the pressure in 33 to be applied against the Whole area at the end of the land 5Ib in assisting relation to the centrifugal force and force of the spring 52 moving the valve plunger to a closing position with respect to the port 54. While the land 5Ia is closing port 54, the land 5Ib is also closing a passage 54h leading to a leak valve 55 having lands 55a and 55h housed in a bore 56 opening with a leak orice 53a into The neck portion between the lands 55a and 55h opens by 55e to an axial bore 55d communicating with the leak chamber 56h. A spring 51 resists upward movement of the valve 55 since the spring is housed in an enlargement 56o of the bore 56, a relief or Venting passage being provided at 56d. 1

When the Valve plunger 36 moves away from the covering relation with respect to ports 3I and 32, there is connection of the supply port 34 amscezoo with 'one' or'tl'ieotherl of'lthezpitchilshiftfports I- and 32 whichconnectionsgiveslrisetoaai momentary `V reduction Ain pressure incthe pressurebline I2 ,lf2 I and -which lis .transmitted -to the chamber 23-of-fthe pressureucontrol valve. The? fall .of pressure there. permi-ts-1the1'11ands-s-5Ia aand'lSIb to-move up slightlyfclosing-osomewhat, iflnot altogether, the ports H54 and 1 5417, thereby :immediately :raising the potentialof pressure in the line =I2, 2I,1 to meetthe1pressuredemands-of the-ports 3-I and'32. 'Iit'isf-an instance inwhich the Valve plunger -36 imoveslupwardl-y .to .connect port =34 with port 3i, as for'increasefpitchshift which usuallyv frequiresthe expenditure-ofmore energy, thenr in addition to lthe increaseoff-pressure provided -by the movement of l-v`alve 5l to closeI the por-ts becauselof-'lessenedpressureon the area of landvlmw'there1-is-appliedthe inuenceof vthe pressure vfromA VI4 through @Swto the under vsideof landilb, or to chamberlf which assists centrifugal landspring force on :the valvel in closing @the-portsi and 54h. VThat results because the pressure applied at the-neck of the valve `5I between -the lands -5Ia and/5111; passes through 5lId-and'5l'e to the chamber'llj Where-it is applied against the VWhole area-of the-land Sil-b and vcancels -out the effect'of the pressure Yfrom 22-uponthe end area of l-andiEIa, presurning Athat fthe pressures inA passages `I 2 and 33 connected by'parts 34- and SI are-equal.

During normal operation ofthe propeller While itisbeing'regulated or-governed bythe distributing'rvalve, there is designedly a bounteous `supply 4ofiiuid under pressure-'being delivered ley-the pump I into-the system, thesupply being in such surplus over what is "neededfor y-eontinuedronspeed-operation that `there Will-beA more'or less a 'continual vdischarge lfrom passages-54a, l56a and '55d'(Fig. 2) -into thereservoir. nIn theonspeed `condition `thereis usually fsulicient cracking of the coveringrelation of land` :3? and -port 3| :that the 'pressure from'port 34 Will-be-'maintained thru port '3|v tothe increase pitch-side 'of Athe servo-motorJ-ML That pressure isfdesigned Yto oppose vthe natural-tendency of the bladeto turn jon its "pitch axis rtoward-a pitch, decreasedA position. Flow :may occur in passage '33to'the neck of valveS'tbetweenthelandsfla andi 51hv and 'through 5151 whennotcompletely covered by landI EI'b, .to :theA neck of; valvebetweenthe lands 55a and 'btolflow t-hroughc and 55d to `chamber 56h Aand-finally :through'the leak orifice 58a. The rate offleakthrough-afis controlled at'two'points. Under medium pressure conditions in chamber 23' the land5'Ib"may-only partly uncover opening 54h such that when an increasing pressure pulse is applied ythroug'hf-ft'ih that pressure Will Workthrough the passagesbld and `5Ic in the chamber Blf to completely -cover the passage Elib. Then the flow to the leak? -valve is completely cut off. If'the pressurein chamber 23 is so high that passage `*5th is Wholly'open then a `pulse of pressure applied-through 33 rmaylflow therethrough to thek neck of the leak valve. There it ows throughc and 55dto the-chamber 58h, and there if Ynot relieved vby owing through the leak ori-ce -Emexerts fagainstthe endface of land Jb to force the valve 55 upward against the Vspring 5L-and in -doing-so-the land 55h atleast partiallyrcuts ofthe flow from passage 54h. In these provisionsthe systempressure is always maintained'atsuch apotential `of -pressure that the blade shift Y'called-for by the distributing valve is `always accomplished.

' The charging 'of the accumulator; 'an'dltheap- 6 plcation of. its .stored energy 'doesi not interfere with the system pressure at any time. By reason ofzthe restriction; 6. charge :of itheV .accumulatorslis retarded untilzthe pressure in 'fthe .line 12,552] .is built .upto a minimum .valuegtthen occurring. by flow.` of fluid underpressurefthrough the restrictioniand check valve .1, to the. storage chamber 63; of .the accumulator. From .the storage Achambertfof theaccumulator the branch Mi leadsto the; accumulator control valve 1Q, 80 through branches. .65,166 thataend. at: a pressure actuated.

valve ill and a pilot'valveiI. respectively. The pressure-actuated valve ..'II .is urged to port/closing positionoyaspring 12,1While a -pressure chamber Z3.has.a cross connection LIllito the pilot valvtezl that controlsaport fadmittingaccumulator pressure :to thechamber 'I3 for shifting the pressure .actuated .valve 'II. Whenrthisfvalue is` actuated it .connects :the accumulator. line 65Lto the prcssurelinel by passage r2I.at1a.point2be tween thelinecheck valve'x2llland thedistributingevalveil. rhe valves 'II andI are-.housedl;in bores .75 and183 respectively, .each having proper ports and connections 'onere/ith another. to effect selected operation "of thecontrol valvefwhenla trip vmember .31% is actuated bythe pilot.

1' In -the specic form of control valve ofrlfig; il, the pressure actuated valve-'I I .provides a large diameter head lIa traversing .the largersection of'the-.-.bore vr'l5 housing `the-springfl .and fis adapted to moveto either-'side ofhaportll'll, openingyinto the passage 124. AI-coned portion IfIb seatslon a shoulder 'I-lb.\.at. the juncturewitha reducedportion Ioa lof .the bore which ends :in the pressure chamber i113 heretofore-mentioned, and disposed at theendvof` apistonfllc onlthe Avalve-5717i 'Thefpassagefsleads from :the charnberl'w' and opens into `a reduced-pcrti-on.183a;.of the bore @3 for the pilot valve, the reduced sportion joining 'the larger portion by a shoulder forming aseat or portr`2'for. a conic .valve'relement-4 SIa urged to -closing position `:by la .spring i235, the valve 8 I having a portion -S I b extending out Aof the bore 'afto engage `the-trip member '84. As the control valve is shown in Fig. Yl, theaccumulator4 pressure `is closed soif lfrcmsthey pressure-line-EI, lbutmay `be connected thereto '.by movement of --the member '.84 to depress rlthe `.valve ^8I uwhich lits -the headla from. ithe port ."3'2. When'that is done,ftheluid-under pressure inthe accumulator if@ may flowthroughltuf,183, '82, Eta, andal -to .the pressure chamber; 13. That pressure acting on the .piston 'flic :pushes the -valve '.l'I against 'the-spring' l2 -to .lift :the coned -part 'IIb vfrom the portliib Vso thati-the accumulator 'pressure in fbranch-s554nay Athen `-1low--into bore IAFia-and-fthrough port 'MIb-.to :the chamber hv on the right sideof the head lla, which--operatesto move the head tothey left hand side of lthe port -`I w opening Ito the passage 24. These-conditionsof the -valve are shown yin. Fig. 3. The accumulator pressure f -is `now directly `connected-tothe line 2 I throughthe elements 64, 65, fajlb, 75h; 'fmand andis--adapted to iiow tothe blade-moving servo-motor as determined-1h51 thepositionof the distributing Ivalve-3i). `Y The `valve l I remains openforthat connection so long astlflere is'loW againstthe righthand side of Ithe head "lla, but-as soon asfthe-ow -stops,the pressure-onropposite vsides-of the head '-'I Ia becomes equala-ndthe Avalvecloses against the `port 'flb under the Y' influence `-ofl :the spring 712,- -the f exposed' area of the-- cone l Ib 4:being -eq-ual r to the area-'fof vthe A'piston 'IIcsuch -that Vthere Ais no moment of force tending to hold the valve 1| open.

In the specific form of control valve assembly shown in Fig. 2, the pressure actuated valve 1| is of cylindrical form having two portions 1|d and 1|e separated by an annular groove 1|f with a longitudinal bleed 1 g connecting each end face, there being provided stop portions 1|h and 1li adapted to engage the opposite ends of the bore so as to form the pressure chamber 13 and a spring chamber 13a housing the spring 12. In the accumulator closing position of the valve 1| the stop 1|h is against the left hand end of the bore 15 so that the portion 1|d closes port 65a from the accumulator and port 10a to the pressure line 2|. The pressure chamber 13 is connected to the bore 83 of the pilot Valve where the port 82 is closed by a cylindrical portion 8|c when the valve 8| is maintained in the set position shown. Spaced from the cylindrical portion 8|c there is a guide land Bld and an abutment portion 8|e engaged by the spring 85 which pushes the valve 8| toward the left as shown to engage a latch 84a on the member 84. In the unlatched position of the valve a stop 8 if in the reset chamber 83a may engage the end of the bore 83 when the valve portion 8 lc uncovers the port 82 which then connects with the groove Slg between the portions 8|c and 8|d to which the passage 66 is always open, thereby connecting accumulator pressure from 66 through 8|g, 82, and 14 to the pressure chamber 13. That fluid connection is made when the member 84 is tripped to release the valve 8| which moves to the left from the illustrated position in Fig. 2 to the position shown in Fig. 4. The accumulator pressure in chamber 13 pushes the valve 1| against the spring 12 until the stop 1li engages the end of the bore 15, in which both ports 65a and 10a are open to the chamber 13 so that accumulator pressure may now iiow from 64 through 65, 65a, 13, 16a, and 24 to the line 2| at a point between the system check valve and the distributing valve 38 to be directed to the blade moving servo-motor. The valve 1| in so moving closes a port 16a and opens a port 1Gb of a passage 16 connecting the reset chamber 83a with the bore 15. In the accumulator closed position of valve 1| the port 16a normally connects with the groove 1|,f of the valve which is also open in that position to a relief port 19h leading back to the reservoir from which the pump takes up its supply. In the connecting position the'ports 1Gb and 16a are both closed, but the port 16h is open to the groove 1|Je which now also opens into a groove 10c along the side of the bore 15 and which opens to the passage 24 by means of a pipe 24a. The chamber 13a is always open to the pressure in 2| and the bleed 1|g communicates the same pressure to the chamber 13, which in the valve closing position is line pressure. In the connecting position the chamber 13a is exposed to accumulator pressure from 24, 24a, and which penetrates along 19e, around 1|f, and through 161) and 16 to chamber 83a where it presses upon the end of Bic to move valve 8| against the spring 85 until the latch 84a drops behind the abutment Ble, thereby closing the port 82 leading to the pressure chamber 13. The accumulator pressure being cut off from the chamber 13 the valve 1I now coasts back to the set position under the action of the spring 12 and the bleed 1 |g. In other Words, the pressure actuated valve 1| continues in the accumulator connecting position so long as the iluid under pressure flows through 65a and 8 10a, which like thel structure shown in Fig. 1 is controlled by the distributing valve 30.

The initial control of the distributing valve 30 is effected by the movement of some member connected with the correlating device 90 embodying a control ring 9| maintained against rotation while the propeller mechanism rotates relative thereto so that shoes 92 and 93 of the rotating device ride in a groove 94. The position of the control ring 9| is controlled by a screw device 95 or otherwise so that the ring may be shifted axially for moving a fulcrum 96 along the length of the lever 39 of the distributing valve 30, and for moving an actuator 91 to start feathering and unfeathering. The lever 39 of the distributor Valve is held in contact with the fulcrum 96 by means of a spring 98, and movement of the fulcrum 96 along the length of the lever 39 determines the effect that centrifugal force will have on the valve 36 and lever 39 moving against the force of the spring 98. In the positions shown in Figs. 1 and 2 the valve 36 is shown in the equilibrium during which the propeller would be operating at a selected speed. If the fulcrum 96 is moved to a new position a new set of conditions will obtain at which equilibriumvwould be established between centrifugal force and the force of spring 98, which gives rise to a different speed of propeller operation. Movement of the fulcrum 96 may be for other than selecting a new speed for propeller operation, such as for feathering or for unfeathering the propellers. That movement involves movement of the fulcrum to a reverse side of the line of force application from the spring 98. If the movement is for feathering the propeller, then the fulcrum will be moved from something like the full line shown to the dotted line position indicated at 96a. Centrifugal force will then be assisting the spring force and the valve 36 will move upwardly to connect supply port 34 with the increase pitch port 3| leading to the servo-motor 40. If the movement is for unfeathering the propeller, then the fulcrum will be moved from the dotted line position at 96a to something like the full line position, Since the propeller is at rest when the fulcrum is moved from the feathering position, there will be no centrifugal force applied to the valve and the spring force will move the valve 36 inward to connect supply port 34 with pitch decrease port v32, leading to the servo-motor 49.

Coincident with moving the iulcrurn into and out of the feathering position the actuator 91 is operable to trip the accumulator control valve 10, to supply the power for eiecting the shift. In Fig. 1 the actuator 91 has a cam 99 operable t0 engage a part |98 of a pivoted lever |9| whose arm |62 swings the member 84 in a manner to depress the part Blb of the pilot valve, and start the iiow of accumulator pressure as has been described. The member is actuated whether the fulcrum is moved either to or from the feathering position. When the fulcrum is moved to the feathered position at 96a the cam 99 will be at the position 99a preparatory to again trip the member 84 when the fulcrum is moved to the unfeathering position. Should feathering be called for at a time when the propeller is rotating at high speed, it is possible that the controlled pressure in the control line l2, 2| and consequently in the bore 15 of the pressure actuated valve 1| is so high that unseating of the valve 8 a would not create sufiicient differential on the valve 1| to open the port 10b, for accumulator pressure flow. In order to have the proper connections available asecfzoo for thatilowwhen the. speed falls far enough to reduc'etheline pressure; in |5,fr a centrifugal re.- sponsive member. |03 isladapted to slide tov a position'behindrthe endof;member1'84 so" as to hold the pilot valve open at the port 82. Aspring |04 withdraws the member|03 when the speed or pressure fallsto apropervalue.. When'the feathering functionis completed,.all of they parts return to. the normalv position .trapping the remainder offluid'lunderY-pressure vin the accumulator;- In-theY form shown in Fig. '2, the actuator 91- 'moves a cam 99' into'contact with the-riser |U5"of the member 84 to rock'it about a pivot '|06 against a spring H11-"tending to maintain the latch 84a in place. Once the latch 84a is withdrawn, the pilot valve 8| moves to they left and stays'there until the shift of the pressure actuated valve II moves-to close the port 16a and connect port 1Gb withA 10c. Therefore high pressure in thelines I2,2| at the start of feathering will eventuallyvfall so low as to present the required diierential on valve H and it will shift when the conditions are right for its completing the function. From the dotted line position 99a shown in eitherview, the Vactuator may be moved toward the full line position for unfeathering, and that movement againetripsthecontrol valve and connects" the' 'accumulator vwith the line as has been described.

Fig. 5 shows an installationl'ofapparatustproviding the fluidcircuitshownfinFig. i-and graphically shows a gear casing or engine nosing from which extends a propeller shaft I I mounted,in1bearings 'I |`2 secured tothe nosing; there being KY.clips IIS secured"them-:on-*between which engages a lug I4 extendingfrom a-sleeve I5 and from `which radially extendsatoothed flange I IB engaged by a pinion I I1 attached to the pump I. The pump I and all of the control elements and connections therebetween are mounted on a plate I|8 supported by the propeller hub ||9 carried by the shaft I II to which it is secured in driving relation by means of splines I2!) or the like. A cover |2| secured to the edge of the plate |I8 encloses al1 of the control elements and provides a reservoir |22 for storing the fluid medium on which the control mechanism works. The sleeve I| extends rearwardly out of the reservoir to make connection with the clips I I 3 and therefore holds the toothed flange IIS against rotation within the reservoir |22 so that rotation of the propeller will cause the pump driving gear II'I to roll around the flange IIe in developing the fluid pressure needed. Outside the cover there is a circular rack |23 having an arm |24 to be oscillated by a rod or wire |25 and in doing so r0- tate a plurality of pinions |26 provided for the screw shafts 95 that operate to shift the control ring 9| as has been described. The hub I9 provides a plurality of sockets |21 each of which pivotally support a blade 43 that is rotated in a pitch changing sense by the servo-motor piston 40, 4|, the rotation of the several blades being equalized by the master gear |28. The accumulator 6|] is mounted on the front of the hub and has its fluid connection 8 leading back through the hub to connect with the control Valve assembly 86 as has been described. A push or pull on the member |25 will select the operating condition desired by the pilot, and will enable him to select the speed at which the propeller will operate, or will make it possible for the pilot to either feather or unfeather the propeller.

While the embodiment of the present invention as herein disclosed, constitutes .a preferred form,

1'10' itis. to beunderstood that` other forms might be adopted.`

What .istclaimed isras. follows l; Hydraulicycontrol `means for an aircraft propel-len. comprising' in combination, a source of fluid 'under pressure anda pressure line for conveying therfluid under pressure to pitch control devices including a fluidY pressure servomotor and a distributing fvalve, a minimum pressure valve? yinfthe linebetween" the source and distributing" valve, ani accumulator vand control valveassemblyv connected to thev line and shunting the minimuml pressure valvewhereby the accumulator may be charged withoutyinterfering withf'the fluid pressure yline tothe pitch control devices'.

2l' Hydrauliccontrol meansxfor an aircraft propeller, comprising in combination, a source of'ili'iid under lpressure including a pump and af pressure' line for conveying the fluid under pressure tov pitch control'devices including ailuid pressure' servo-motor andAv 'a distributing valve, pressure storing means including an accumu; lator,lv means intheline for insuring a minimum operating pressure tovb'e delivered to the accumul'ator,` variable pressure control means connected to the-linefor controlling the pressure fluid applied bythe distributing valve in accordance with the powerneeds ofthe servo-motor, meansconnectingthe accumulatorto the pressure line hydraulically ahead ofthe minimum pressure means, an' accumulator y control' valve assembly hydraulically'connecting the accumulator'to the pressure lineat` apoint hydraulically after the variablepressure control valve, whereby the regulatediluid'- pressure --from the pump distributed by" thedistributing valve Vmay be supplemented bi1-accumulator pressure.

3. The combination set forth in claim 2 wherein the accumulator is charged through a restricted passage and check valve exposed to source pressure.

4. The combination set forth in claim 2, wherein the variable pressure control means includes an equal area valve controlling a constant bleed of fluid pressure from the pressure line to the pitch increasing side of the servo-motor.

5. Hydraulic control means for an aircraft propeller, comprising in combination, a source of fluid under pressure and a pressure line for conveying the fluid under pressure to pitch control devices including a fluid pressure servomotor and a distributing valve, a fluid pressure accumulator and connections to said source for charging the accumulator independent of said pressure line, valve means in said line and exposed to the pressure source for establishing a minimum pressure potential in said accumulator, pressure control means connected with said pressure line for determining the maximum potential of said line, a check valve in said pressure line operable to admit controlled pressure to the distributor valve, and accumulator control means for applying the pressure charge of the accumulator to the pressure line at a point between the said check valve and the distributing valve, so that the accumulator pressure may be added to the pressure line without being altered by the pressure control means.

6. The combination set forth in claim 5, wherein the accumulator control means comprises a hydraulically operated Valve exposable to the pressure of the accumulator and to the pressure line, and control valve means for selecting whether the accumulator pressure or the line pressure shall be applied to the hydraulically operated valve, and means whereby the accumulator pressure applied to the hydraulically operated valve will move that valve to a position connecting the accumulator pressure to the line and maintain that valve in the connecting position so long as accumulator pressure flows into the pressure line.

'7. The combination set forth in claim 5, wherein the accumulator control means comprises a hydraulically operated valve eXposable to the pressure of the accumulator and to the pressure line, and control valve means for selecting whether the accumulator pressure or the line pressure shall be applied to the hydraulically operated valve, and means whereby the accumulator pressure applied to the hydraulically operated valve will move that valve to a position connecting the accumulator pressure to the line and maintain that valve in the connecting position so long as accumulator pressure iiows into the pressure line, said last named means including a pivoted lever for actuating the control valve, and a speed responsive member operable to hold the lever in control valve open position.

8. The combination set forth in claim 5, wherein the accumulator control means comprises a hydraulically operated valve exposable to the pressure of the accumulator and to the pressure line, and control valve means for selecting whether the accumulator pressure or the line pressure shall be applied to the hydraulically operated valve, and means whereby the accumulator pressure applied to the hydraulically operated valve will move that valve to a position connecting the accumulator pressure to the line and maintain that valve in the connecting position so long as accumulator pressure iiows into the pressure line, said last named means in. cluding a spring and an opposing piston face on said hydraulically operated valve exposed to the accumulator pressure during flow from said accumulator.

9. The combination set forth in claim 5, wherein the accumulator control means comprises a hydraulically operated valve exposable to thel pressure of the accumulator and to the pressure line, and control valve means for selecting whether the accumulator pressure or the line pressure shall be applied to the hydraulically operated valve, and means whereby the control valve means is spring pressed to normally condition said hydraulically operated valve to interrupt connection between the accumulator and the pressure line, manually operated means are provided for tripping the control valve means for applying the accumulator pressure to the hydraulically operated valve for connecting the accumulator pressure with the pressure line, and means for resetting the control valve means preparatory for a succeeding connection of the accumulator with the pressure line.

RICHARD E. MOGRE. DAVTD ALLEN RICHARDSON.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,480,257 Gerlinger Jan. 8, 1924 2,264,375 Hill et al Dec. 2, 1941 2,392,471 Fox Jan. 8, 1946 2,424,749 Haines July 29, 1947 

